Protective device



P. R. FORTIN. PROTECTIVE DEVICE.

APPLICATION FILED OCT-21. I919.

Patented Dec. 27, 1921.

Inventor: Paul R.Fo'rt,in,

His afittorne g.

UNITED STATES PATENT OFFICE.

PAUL It. FOR'IIN, OF

SCHENEGTADY, NEW YORK, ASSIGNOB TO GENERAL IH'JEGTRIG COMPANY, A CORPORATION OF NEW YORK.

PROTECTIVE DEVICE.

Specification of Letters Patent.

Patented Dec. 27, 1921.

Application filed October 21, 1919. Serial No. 332,167.

To all whom it may concern.

Be it known that I, PAUL R. FORTIN, a

citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Protective Devices, of which the following is a specification. My invention relates. to protective devices and particularly to relays and has for its object to provide a relay for the protection of transmission lines which is operative in response to unbalanced current conditions to open the circuit of that line causing the unbalancing and which comprises a structure, to be hereinafter specifically set forth, which is an improvement in devices of similar character heretofore known.

The relay of my invention is applicable to the protection of transmission lines against unbalanced current in similar phases such as would be occasioned by a fault in one of the lines. As the current increases in the lines, the difl'erence in current in the lines must increase before the relay will operate. This compensates for a normal inherent difierence in impedance in thelines. The relay operates to open the circuit of the line carrying the greater current and, comprises a movable contact carrying or circuit controlling member operative in one direction to closethe tripping circuit for one line and in the opposite direction to close the tripping circuit for another line. The circuit controlling member is controlled by three solenoids, a small solenoid connected to each end of the controlling member and acting to restrain or hold the member locked in normal position, and a larger'solenoid connected to the controlling member intermediate the ends thereof. This larger solenoid is normally inoperative butis operative by differential current or the difference in current in the two similar phases, to move the circuit controlling member against the restraining action of the other two solenoids into contact engaging position, when the differential current becomes great enough to overcome the weaker of the two solenoids.

The novel features. which I believe to be characteristics of my invention will be definitely indicated .in the claims appended hereto, while the features of construction and mode of operation will be understood by reference to the following description taken in connection with the accompanying drawingwhich shows the preferred embodiments. of'my invention and in which- Figure 1 is a front view, partly in section, of a relay embodying my invention; Fig. 2 is an end view of the relay shown in Fig. 1, and Fig. 3 is a diagrammatic illustration of the application of my relay to the protection of transmission lines.

In Fig. 1 is shown a relay embodying my invention comprising a movable contact carrying or circuit controlling member 1 carrying a movable or bridging contact 2, best shown in Fig. 2, adapted to be moved into engagement with either of two sets of fixed contacts 3 or 4. Fixed contacts 3 control the trip circuit of one feeder or transmission line and contacts 4: control the trip circuit of another line, as will be described more in detail hereinafter. Pivotally secured at each end of the circuit controlling member 1 are plungers 5 and 6 of electro-responsive means or solenoids 7 and 8 respectively. Solenoids 7 and 8 act to attract their plungers. 5 and 6 respectively, to hold the circuit controlling member 1 locked against movement, the solenoids acting as restraining or locking means. To prevent vibration of the circuit controlling member 1 due to slight inequalities of the forces exerted by solenoids 7 and.8, the plungers 5 and 6 thereof are provided with collars 9 and 10 respectively, which engage with stops 11 and 12 of non-magnetic material to limit the distance which the plungers 5 and 6 can be moved in attracting direction. When the solenoids are energized, the plungers are held with collars 9 and 10 in engagement with stops 11 and 12 and the member 1 is correspondingly locked against movement. Movable contact 2 is thus held locked or restrainedin position intermediate fixed contacts 3 and 4.

Pivotally secured to the central portion of circuit controlling member'l is a plunger 13 of a larger solenoid 14 located intermediate solenoids 7 and 8. The plunger 13 is secured to member 1 by means of a clevis coupling 15 and a rod 16. The rod 16 is movable by plunger 13 in tripping direction against the action of a biasing means or spring 17. The clevis coupling 15, is secured to the circuit controlling member 1 by means of a pin 18 movable in a slot 19 provided in the member 1. The osition of the plunger 13 to operate at d1 erent ourhence in similar rent values, is adjustable by means of the rod 16 upon which the plunger is threaded.- The position of the plunger being indicated by the calibrating tube 20, as is well known in the art. Solenoid 14 serves as an actuating means and exerts a force opposite to that. exerted by the locking coils 7 and 8, and in a direction to overcome one or the other of the locking coils and move the member 'linto contact closing position.

The application of the relay of my invention to the protection of transmission lines is best shown in Fig. 3 in which the relay is connected between similar phases of two transmission lines 21 and 22 shown, for the purpose of clearness in one line diagram only. These lines or feeders 21 and 22 are connected to the main bus or feeder 23 through the usual type of circuit breakers 24 and 25. The circuit breakers 24 and 25 are adapted to be tripped by the closure of their trip coil circuits, the closure of contacts 3, controlling the tripping circuit of switch 25, and contacts 4 that of switch 24. Connected to similar phases of each feeder 21 and 22 are transformers 26 and 27, re spectively, the secondaries of which are con nected ina series circuit including the look ing or restraining coils 7 and 8. Connected across this series circuit, in a manner to receive the difference in current between that in the two transformer secondaries and phases, is the actuating coil or solenoid 14.

With balanced current on similar phases of lines 21 and 22, solenoids 7 and 8 receive equal currents and there is no differential or difference in current to flow through actuating solenoid 14. Thus solenoids 7 and 8 hold their plungers 5 and 6 with their collars 9 and 10 tightly against stops 11 and 12 and maintain the circuit controlling member 1 locked against movement. So long as the currents are substantially equal or balanced.

in the two feeders 21 and 22, the relay is in- 5 operative. Let us assume, due to a fault or some other condition on one line, for instance, line 22, that the currents in similar phases of feeders21 and 22 are not substantially equal, as thatin the transformer circuit there is an unbalanced current, of for instance, 10 amperes. In this case, locking coil 8 exerts a restraining influence upon its end'of circuit controlling member 1 corresponding to the current in its transformer secondary '26 and locking coil 7 exerts a restraining influence on its end of controlling member 1 corresponding to the current in its transformer secondary 27. If the unbalancing is due to feeder 22, the current in secondary 27 is greater than that in secondary 26 and consequently solenoid 7 exerts a greater restraining action than solenoid 8. The unbalanced current, which'we have assumed 1s 10 amperes, flows through solenoid ber 1.

'22 to .carry relatively heavy overloads with 14 and it exerts a force to raise it plunger 13 and hence the circuit controlling member '1 against the restraining action of solenoids 7 and 8. The result is, that the force exerted by solenoid 14 overcomes the restraining force exerted by the weaker of the two locking coils 7 and 8, in this case, coil 8, and moves the circuit controlling member 1 about its pivotal connection to plunger 5 of solenoid 7, the pin 18 of the clevis coupling 15 sliding to the left in opening 19 of the mem- The member is thus rocked to the right by solenoid 14 until the movable bridging contact 2 engages fixed contacts 3 and closes the trip coil circuit for switch 25, thus opening the line causing the unbalancing or that line having the greater current. Upon the opening of the feeder 22, the plunger 13 of solenoid 14 returns to normal position aided by spring 17, and returns member. 1 to initial position. Obviously, the greater the current in each of the lines 21 and 22, the greater the restraining effects exerted by solenoids 7 and 8 and, therefore, the greater the difference in currents must be between the lines 21 and 22 for the solenoid 14 to overcome the restraining effect of the weaker one of the two restraining solenoids 7 and 8, that is, the relay will permit the lines 21 and a greater unbalancing or difference in currents than is required to operate the relay in the case of lighter loads. This action of Y the relay is desirable and important as ordinarily the inherent impedances of the lines differ and there is therefore a difference in current depending upon the respective impedances and proportional to the currents in the lines.

' For three phase circuits, it is understood that one of my relays is connected between similar phases of eachcircuit. It is also understood that the application of my relay is not limited to the two feeders but may be, used with three or more feeders by suitably balancing two feeders together in groups. I

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together 11 with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and

that the invention can be .carried out by I forces on the ends of said member to hold [the same against movement, and means cooperating with said member intermediate the ends thereof operative in response to a predetermined unbalancing of the forces exerted on the ends of said member to move the same into circuit controlling position.

2. In a relay, the combination with a circuit controlling member movable to control two circuits,'restraining means normally exerting balanced forces on the ends of said member to prevent movement thereof, and an electro-responsive means cooperating with said member intermediate the ends thereof when the forces exerted by said restraining means become unbalanced to overcome the weaker of said restraining means and move said member to control the circuit corresponding to the stronger of said restraining means.

3. A relay comprising a movable circuit controlling member, restraining means cooperating with each end of said member to. hold it locked against movement, actuating means cooperating with said member intermediate the ends thereof tending to move said member into circuit controlling position, saidactuating means operative when the restraint exerted by said restraining means is unbalanced to overcome the restraint of the weaker of said means.

4. A relay comprising a movable circuit controlling member, two solenoids, plungers for said solenoids pivotally secured to each end of said member and adapted in attracted position to hold said member against movement, means limiting the movement of said plungers in attracted position, a third solenoid acting in response to an unbalanced attractive force exerted by said two solenoids for overcoming that of the weaker and moving said member to circuit controlling position.

5. A relay comprising a movable circuit controlling member, electroresponsive means pivotally secured at each end of said member exerting forces normally adapted to hold said member against movement, and actuating means pivotally secured to said member intermediate the ends thereof for moving said member to circuit controlling position, said actuatingmeans being inoper' ative until the restraining effect of one of said electro-responsive means is substantially weaker than the other.

. 6. A relay comprising an actuating solenoid, two restraining solenoids, a circuit controlling member differentially operative, thereby, and two sets of contacts controlled by said member, said member being held inoperative while the restraining effects exerted by said restraining solenoids are substantially equal but difierentially movable by. said actuating solenoid to engage one of said sets of contacts when the restraining efiects exerted by said restraining solenoids are substantially unequaL' 7, A protective system of-the class described comprising two transmission lines, means for .interrupting the circuits of said lines, a movable circuit controlling member adapted to be operated to control said interrupting means, means for holding said member inoperative when current conditions in said lines are balanced, and electro-responsive means pivotally related to said member intermediate the ends thereof operative in response to unbalanced current conditions in said lines to move said member to control the circuit interrupting means i of the line causing the unbalancing.

8. A protective system of the class de-' scribed comprising two transmission lines, means for interrupting the circuits of said lines, a circuit controlling member adapted to be operated to control said interrupting means, two restraining solenoids operative in response to balanced currents in said lines to hold said member stationary, and an actuating solenoid operative in response to unbalanced currents in said lines to overcome one of said restraining solenoids and move said member to control the circuit of the line causing the unbalancing.

9. In combination with two transmission lines, means for interrupting the circuits of said lines, a differentially operated circuit controlling member adapted to control said interrupting means, two restraining solenoids responsive to currents in said lines for exerting balanced restraining forces on said member as long as the currents in said lines are substantially equal, and an actuating solenoid intermediate said restraining solenoids operative in response to a diiference in the currents in said lines to overcome the weaker of said restraining solenoids and move said circuit controlling member to control the interrupting means corresponding to the circuit ofthe line having the greater current.

10. A protective system comprising two transmission lines, means for interrupting the circuits of said lines, a circuit controlling member adapted to be operated to control said interrupting means, restraining solenoids pivotally related to said member operative in response to balanced currents in similar phases of said lines to hold said member inoperative, and an actuating solenoid pivotally related to said member intermediate said restraining solenoids operative in response to unbalanced currents in said similar phases to render said member selectively operative to control the circuit interrupting means of the line carrying the greater current.

11. The combination with two transmission lines, of means for interrupting the circuits of said lines, a circuit controlling member rotatable in opposite directions to control said interrupting means, restraining solenoids pivotally related to the ends of said member operative in response to balanced currents in similar phases of said lines to hold said member stationary, an actuating solenoid pivotally related to said member intermediate the ends thereof operative in response to unbalanced currents in said similar phases selectively to rotate said member about said pivoted ends to control the circuit interrupting means of the line causin the unbalancing.

12. he combination with two transmission lines of a circuit interrupting means for each of said lines, a circuit controlling memwhich is a measure of the difierence in the currents of said lines whereby upon the occurrence of currents of different valuesv in said lines said member is selectively moved to control the interrupting means of the line carrying the greater current.

13. A relay comprising a circuit controlling member movableabout either of its opposlte ends as a pivot, circuits controlled by the movement of said member in both directions, electroresponsive devices pivotally connected at opposite ends of said member exerting a restraining force to hold said member against movement, means operative when said devices exert substantially unequal restraining forces to overcome that device exertin the weaker force and move said'member a out its pivotal connection to the device exertin the stronger force, and a, circuit controlfizd by the movement of said member to interrupt the'circuit of that device exertin the stronger force.

n witness whereof, I have hereunto set my hand this twenty-first day of October,-

7 PAUL R. FORTIN. 

